Ear telephone



July 14, 1925.-

H. SELL EAR TELEPHONE Filed nec. 14.. 1922 manually 14,1925.

Hummm SEL-L, or BE'nLm-criAnLo'rrENsUne, dmanr, assrenona'o HALsxE, AKTIENGESELLSCHAFT, or sInunNssTAnT, Naan BERLIN, am

GERMAN ('IOBPORATION` `1 ATENT orne F..l l

Sill-I IHC Een. TELEPHONE.

Application iled December 14, 1922. Serial Fo. 006,9162.

To' all 'whom it may concem:

Be itknown that I, HELMUTH SELL, a citizen of the German Empire, residing at Beri lin-Charlottenburg, Germany, have invented certain new and useful Improvements in Ear Telephones, of which the followingA is a specification.

This invention 4relatesto improvements in telephones of that ty e, which are attached directly to or inthe uman ear and whlch are therefore rather small. Such ear teleor as head telephones by employees bf telephone oilices or other stations where permanently telephonie communications or signals are received.

Telephones of vided with a diaphragm of animal skin,

preferably gold-beaters skin, onto which a small iron armature is glued. Owing to the smallness of such diaphragme it is rather improvements in the construction of telephones of this character for the purpose of obtaining improved speech modulation. Tla nagnet used is of the form of the so- -c'a e of the 1ron cylinder is turned in for a cerl cylinder, terminating closely adjacent to the taindistance towardsthe central axis ofthe central core of the' magnet so that only a verysmall air gap remains to be bridged by\ the iron phragm. The result of this-construction is that the diaphragm armatuii need only be very small owing to thethusifobtained favorable magnetic conditions. Asa conseuence of the vlightness of the armature, the

iaphragm itself vcan very easily follow the vibrations impressed upon the armature by the arriving s eech currents.

Secondly, t e purpose of the present invention is to construct the telephone in such manner that it ca'n be easily assembled for g-liiantity production. For this purpose the aphragm is held in place by the magnet the diaphragm. phones are used by persons hard of hearing, Th

such type are generally procult to properly tension` pot magnet in which the upper rim" armature attached to the dia-1;; glued to its center, its outer edge being bent over and clamped-*betweenthe wall of cas- 1 and a rimof disc 5.

armature 7 to said' annular part 13.l

casing, being provided for automatically pressmg the magnet against the diaphragm. Lastl the invention relates' to limproved means for effecting an automatic maintenance of the stress imparted to the diaphragm, for which purpose the tension ring is arranged dlrectly onl the magnet acting upon the diaphragm while said magnet is slidably. lo-

cated and influenced by .a spring which presses Vthe same and the ytension ring against e` accompanyingl drawing represents vsuitable consti-notional forms of the improved arrangement, on an enlarged scale; s Flg. 1 is a central` longitudinal section through a telephone adapted for persons hard of hearing;

Fig. 2 shows* a` connection diagram for saidtelephone, in which an induction coil serves for transmitting the speaking currents; Fig. '3` shows art of thetelephone with a modification ci) the diaphragm tensioning means; and

Fig. 4 shows a further modification of the tensioning means.

The telephone is mounted within a-casing 1 having a funnel-shaped front end 2 of in- .sulating material to be introduced into the ear duct. Said front end contains a duct 3 for the sound waves, which is lined by a metal tube 4 xed at itsinner end to a disc 5 within said casing', which disc serves at the same time for the attachment of the diaphragm 6. The latter Iconsists of gold-V eaters skin and hasa soft iron armature 7 -v with its bottom piece 11 vscrewed into an outer cylinder 12, which has an upper inwardly projectin annular part 13 facing the projecting en' of the shank 9 in such a way that the magnetic lines of force run lfrom the central shankA 9 over the diaphr e outer cylinder 12 of the magnet and the bottom' iece 11 are, at"`least at one point, pro- 10 i vide with a longitudinal slot 14 in order f neV 2, the circuit of the magnet coil is separated from that of the microphone 15 by an induction coil or by a transformer 17, it is essential that in the circuit of the telephone coil a small auxiliary1 battery` 18 is arranged which supplies the exciting current for the telephone ma et. 4

The magnet 12 is slidablein axial direction within the casing 1 and carries on its upper end cylindrical ridge 19 which bears against the diaphragm 6 in such a way that the latter is pressed inwards and tensioned withinthe portion encircled by ridge `19 in a particularly favourable manner for the sound production. The pressure `against the diaphragm 6 is produced by means of a pressure spring .20. interposed between the bottom piece 11 of the magnet and the bottom 21 of the casing 1, which bottom is preferably threadedinto the casing for the purpose of easily regulating the tension of said spring. y

It 1s o importance that the pressure spring is not tuned to the vibrations of the diaphragm 6, for which purpose it must be so chosen thatvits natural frequency lies beyond the frequency range of the diaphragm.V Furthermore, the spring 2Ol can be prevented from participating-in the vibrations of the diaphragm 6 by connecting large masses thereto. the pot-shaped magnet itself can be used as such a large masst he spring being then iirmly connected with the ottom .piece 11. The spring may consist of metal or of an india-rubber cushion.

The wire-cable 22 for the telephone coil 10 is led to outside the casing 1 through a boring 23 in the wall of the latter." In case the bottom 21 is lixed in the casing 1, boring 23 can also be provided in this bottom.

Fig. 3 shows a. modification of the tension ring, which, in this example, is formed of a thin wire split-ring 28, which, when bein inserted, automatically takes-up its centra position. This construction has the advantage that, with) the extremely small dimensions of the parts, a wire ring .can be' more exactlydimensioned as to its thickness than the projection 19 made by turning?.

-The distance of the diaphragm amature from-the magnet `9, 13v amounts, to fractions of one millimeter only.

.Fig. 4. shows a further modification of the tensioning means for the diaphragm 6:

. In the upper part of the casing 1 shown, a

cylinder 24' is inserted, in which V the dia- In this connection,o

-central core terminatin phragm v6 isclamped fast'by means'of an' inner ring 2 5. The latter has internal screwthreads 26, into which screws an annular Q stressing member 27 which bears against the diaphragm 6 and imparts to the same the necessary tension within the art encircled. by it. The tension of the dlaphragm 6 is 1n this case adjustable and controllable.

The'magnet (not shown) is, in this example, immovably yix'ed in the casing 1. While this construction has the advantage of great simplicit the construction shown in Fig. 1 affords tiie possibility of automatic control of the diaphragm tension.

The invention is not limited to theconstructions shown by way of example but it includes all further possibilities of construction lying within its scope.

What Iclaim, is:

1. An auricular telephone comprising in combination a casing, a diaphragm disposed within said casing, a magnet slidable in axial direction Within said casing, and yielding means for pressing said magnet against said diaphragm near its eriphery.

2. An aurlcular telephone comprising in combination a casing, 'a pot sha ed magnet 1n. axla alignment disposed in said casin therewith, said magnetghaving a central core and having its rim turned inwardly toward said core, a diaphragm of non-magneticmaterial'fastened within said' casing and having an iron armature attached to it throughout the whole surface of the latter, said armature bridgingk the air ap between the end of said shank and saidg turned rim.

3.- An auricular tele hone comprising in combination a cylindrical casing having a central sound passage at one end, a pot shaped magnet slidingly disposed in said casing, said magnet havin a central core and having its rim turned inwardly toward said core, a diaphragm ofnonmagnetic material fastened within said casing adjacent to said sound passage and havingl an iron armature attached to it through the whole surface of the latter, said amature bridging the air gap between the' end of said shank and said turned rim, said casing having a bottom at its other end, and a spring disposed between said bottom and said magnet, tending to force the latter against said diaphragm, said magnet havingmeans for bearing against said diaphragm near its periphery. r

4. An'auricular telephone comprising -in combination a cylindrical casing having a central sound passage at one end, a pot shaped magnet consisting of acylindrlcal ,portion having its vupper rim turned toward the cylinder axis, a bottom portion threaded into the other cylinder end and having a adjacent to said inwardly turned rim an an energizin coil lll disposed on said Gore, the magnet cyllndersf,

wall havin a longitudinal'slot and the bottoln of sai -magnet`having a radial slot, a diaphragm of non-magnetic material mounted in said casing adjacent to said sound passage and having an iron armature attached to its central portion, said armature bridging the air gapbetween said magnet core and its in-turned rim, and means'for holding said magnet in said casing in operative position relatively to said armature.

5. An auricular telephone comprising in combination a cylindrical casing having a central sound passage at one end, a ot shaped magnet consisting of a `cylindrical portion having its upper rim turned toward the cylinder axis, a bottom portion threaded into the other cylinder end and having a central core' terminatin adjacent. to said inwardl turned rim an an energizin coil dispose on said core, the magnet cylinder passage and havin wall h avin a longitudinal slot and the bottom of said magnet having a'radial slot, a diaphragm of non-magnetic material mounted in said casing a jacent to said sound an iron armature attached to its centra portion, said armature bridging the Aair gap between said magnet core and its in-turned rim, the upper portion of said magnet having an annular ridge ,adapted to bear against said diaphra 1nnear its periphery and a spring disposed e- -tween said magnet and the bottom of the casing to force said ridge against said diaphragm, the bottom of said casing being adjustable tovary the pressure of said magnet against said diaphragm.

In` testimony whereof I aix my slgnature.

HELMUTH SELL. 

